Remember in math class how our teachers would always try to find ways to get the concept of exponential growth to really sink in? Apparently, most of us didn't really get it. I don't think its our math teachers' fault - our minds have a tough time conceptualizing that kind of growth. As the video below from Population Action International also shows, most people really don't understand the systemic implications of this kind of growth when it comes to population, sustainability and an integrated global economy. Don't forget that population is only one component of the "double explosion" of population and economic growth in the developing world. These are huge underlying drivers in the urgency for us to move towards sustainability as quickly as possible.
We hit 1 billion in 1804; 2 billion in 1927; 3 billion in 1960; 4 billion in 1974; 5 billion in 1987; 6 billion in 1999 and now 7 billion in 2011. Of course it's very difficult (technically impossible) to forecast population growth; but in general the rate of growth is expected to slow. Policy measures, demographics, disasters will all likely play a part. But regardless if we hit 9 billion or 11 billion, we already now need to re-think how we meet our needs in ways that are equitable and effective if we're going to navigate the coming century with any measure of grace.
How Many People Are In the World Today? from Population Action International on Vimeo.
Read more on this topic at this related article on Grist.